Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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259 FXUS61 KGYX 190220 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1020 PM EDT Thu Jul 18 2024 .SYNOPSIS... Much drier air will continue to filter into the region through tonight with temperatures in many locations falling to the coolest values in over two weeks. A dry and seasonable pattern is expected through the upcoming weekend and into early next week. Outside of a few mountain showers Saturday night...the next chance for precipitation across the area does not arrive until next Tuesday in the form of showers and thunderstorms ahead of a cold front. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1020 PM Update...No changes to the going forecast. Everything remains on track. 630 PM Update...Very little change to the going forecast. A fair weather night will be hard with diminishing winds with low temps and dewpoints lower than previous nights. Late valley fog is likely. Previously... The long-awaited drier airmass has arrived in the wake of the cold front that crossed the area this morning. Dewpoints are currently in the 50s for most of the area with the exception being Augusta and Midcoast regions, where dewpoints are still holding in the 60s. A couple of light showers will be possible later on this afternoon into early this evening, mainly across far northern areas with dry conditions across the rest of the area. Going into this evening and tonight, the cu field will diminish and with winds becoming light, the mostly clear skies will allow temperatures to cool off nicely. The dewpoints will be a pretty good proxy for lows with coastal areas ranging from the upper 50s to lower 60s with most in the 50s across inland areas. A few of the northern valleys could reach the upper 40s if it stays clear enough, but some guidance is showing a slight increase in cloud cover across the north, potentially limiting cooling. Regardless, it will be a stark difference from the last couple of weeks. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/... The much drier, subsident airmass will be fully in place on Friday with high pressure over the region. As a result, skies will be mostly sunny with no rain in the forecast. While it still be warm out (highs in the low-mid 80s south of the mountains), it won`t be nearly as humid with good mixing, which will bring afternoon dewpoints down into the low-mid 50s. Winds will become light in the evening and persist into Friday night, and with clear skies, good radiational cooling is forecast. A few southern/coastal areas may stay closer to 60 degrees for lows, but in general overnight lows are expected to be in the 50s and even into the upper 40s in some of the northern valleys. Patchy valley fog is also possible. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... High Impact Weather Potential: Minimal through early Tuesday. Chances for showers and thunderstorms increase for Tuesday- Thursday though confidence is low on any severe weather/hydro threats at this range. --Pattern and Summary-- The longwave pattern is expected to remain rather stable through the long term forecast period with a substantial longwave ridge located along the spine of the Rocky Mountains with troughs on either side of this over the eastern Pacific and eastern North America. This will keep the flow aloft generally from the west northwest or west with H5 heights and T8s pretty close to...or just above seasonal norms. Through early next week...the modified Canadian airmass will keep the weather quiet and dry. By the middle of next week...the eastern trough will reload as energy drops into the Great Lakes region...allowing our flow to back southwesterly and allow a frontal system to move through the region to end the forecast period with what will likely be the most active portion of the forecast weather- wise. --Daily Details-- Saturday through Monday: The period opens with westerly flow aloft ahead of a southward-sinking cold front. Temps aloft will be warm...reaching +14-16C which would support highs in the lower 80s in the mountains with mid/upper 80s to the south and east. The cold front crosses the area Saturday night with a few mountain showers....but frontal timing and thinning moisture plume suggests little overall rainfall. Drier and somewhat cooler air sinks in from the north for Sunday...with decreasing clouds and mountain high temperatures in the 70s. Further south...T8s won/t change too much from on Saturday...and therefore 80s are again expected for highs. The drier airmass will allow for more substantial cooling Sunday night with some mountain valley locations likely reaching the upper 40s while 50s to just above 60 is likely further south. High pressure remains in control through Monday with some weak moisture return as the flow aloft begins to back ahead of the next shortwave/cold front dropping into the Great Lakes region. Generally neutral temperature advection should allow for similar daytime highs...mid/upper 70s in the mountains and 80s to the south. Tuesday through Thursday: The second half of the long term forecast turns more active as the eastern trough initially reloads over the Great Lakes...with a positive tilt allowing the flow over the northeast to turn more southwesterly...allowing for building moisture. A weak front dropping into the region Tuesday may spark some showers and thunderstorms with this trend continuing through Wednesday as the flow remains generally parallel to the front causing it to stall and service as a llevel focus for lift. Global ensembles differ on the eventual evolution of the upstream positively tilted trough across the Mississippi Valley and additional shortwave energy diving out of Canada. With the likelihood that the overall trough axis remains west of our longitude through Thursday will necessitate a continuation of shower/storm chances with building humidity but temperatures close to seasonal norms with clouds and precipitation potential. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Short Term...A couple of light showers may develop through the duration of the afternoon, but coverage is much too low for any TAF inclusion. Otherwise predominantly VFR through Friday night, but valley fog may develop tonight and again Friday night, potentially impacting HIE and LEB. Long Term... VFR conditions should persist through Tuesday morning with some morning fog possible each morning at HIE/LEB. Tuesday afternoon will bring a chance of restrictions given a chance for showers and thunderstorms. && .MARINE... Short Term...SCA conditions are not expected through Friday night. High pressure builds toward the region tonight in the wake of the cold front that crossed the waters early today. This will shift winds to N/NW this evening, which will stay through Friday morning. These will switch back to more onshore by Friday afternoon with the development of the seabreeze and high pressure becoming centered south of the waters. Light southwest flow continues through Friday night. Long Term...Winds/waves are expected to remain below SCA levels through the long term forecast period Saturday-Tuesday. Thunderstorms are possible over the waters by Tuesday afternoon. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...Ekster SHORT TERM...Combs LONG TERM...Arnott AVIATION... MARINE...